(1) Field of the Invention
The present invention relates to a broadcast signal receiving apparatus, and more particularly to a digital broadcast signal receiving apparatus that receives a plurality of transport streams.
(2) Description of the Related Art
A broadcast signal receiving apparatus uses a conditional access system in order to receive a pay-TV. Conventional conditional access systems include a system in which a transport stream received by a broadcast signal receiving apparatus is transmitted to a detachable conditional access descrambler apparatus which descrambles the transport stream protected by conditional access in order to provide access to such transport stream, and the resulting transport stream is returned to the broadcast signal receiving apparatus. This technology is standardized in detail in OpenCable (TM) HOST-POD Interface Specification (OC-SO-HOSTPOD-IF-112-030210). FIG. 1 is a diagram showing the construction of a broadcast signal receiving apparatus to which a conventional conditional access descrambler apparatus is attached. The conventional system is configured on the assumption that there exits one tuner 9501. In such system, a transport stream inputted to the tuner 9501 is directly provided to a conditional access descrambler apparatus 9511, which then descrambles such input transport stream protected by conditional access and provides the resulting stream to a TS decoder 9502. The TS decoder 9502 selects necessary information from the transport stream, and sends it to an AV decoder 9503. Out of the received information, the AV decoder 9503 sends audio data to a speaker 9504 and video data to a display 9505. The CPU 9506 controls each device. Information required by the CPU 9506 to operate is stored into a primary storage unit 9508 and a secondary storage unit 9507, as well as into a ROM 9509. Furthermore, these operations may be executed in response to commands from an input unit 9510.
In addition to the above, the following technique is disclosed in Japanese Patent application No. 11-118748: in order to share a result of conditional access among a broadcast signal receiving apparatus, a conditional access descrambler apparatus, and a digital multimedia device that are connected via an IEEE1394 serial bus, the bandwidth is reduced by removing data that is not necessary for the processing of the conditional access descrambler apparatus, when the broadcast signal receiving apparatus transmits a transport stream via the IEEE1394 serial bus.
However, with the conventional technology in which the broadcast signal receiving apparatus passes a received transport stream to the detachable conditional access descrambler apparatus, which then descrambles such transport stream protected by conditional access and returns the resultant to the broadcast signal receiving apparatus, there is a problem that a plurality of transport streams cannot be processed simultaneously in an appropriate manner.